Endocrine System and Hormones Quiz
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Questions and Answers

What is the primary function of progesterone during the luteal phase of the menstrual cycle?

  • Stimulates ovulation
  • Promotes spermatogenesis
  • Prepares the endometrium for a fertilized ovum (correct)
  • Increases LH secretion

    • Which cells produce testosterone in the testes?

  • Sertoli cells
  • Gamete cells
  • Interstitial cells
  • Leydig cells (correct)

    • How does inhibin regulate FSH secretion?

  • By completely inhibiting LH
  • Through positive feedback
  • By a negative feedback mechanism (correct)
  • By stimulating its production

    • What is a major consequence of hyperprolactinaemia?

    <p>Inhibition of GnRH release</p> Signup and view all the answers

    Which of the following is NOT a cause of hyperprolactinaemia?

    <p>Increased FSH production</p> Signup and view all the answers

    What role does dihydrotestosterone (DHT) play in the body?

    <p>Converts testosterone to a more potent androgen</p> Signup and view all the answers

    What effect does chronic kidney disease have on prolactin levels?

    <p>Reduces plasma prolactin clearance</p> Signup and view all the answers

    LH and FSH have an impact on which testicular function?

    <p>Stimulating testosterone production</p> Signup and view all the answers

    What is the average age at which menopause occurs?

    <p>50 years</p> Signup and view all the answers

    Which hormone concentration is expected to increase after menopause?

    <p>FSH</p> Signup and view all the answers

    What defines primary amenorrhoea?

    <p>Menstrual cycles have never occurred</p> Signup and view all the answers

    What is a common cause of secondary amenorrhoea?

    <p>Menopause</p> Signup and view all the answers

    What happens to plasma progesterone concentration in the absence of ovulation?

    <p>It remains low</p> Signup and view all the answers

    How is hypergonadotrophic hypogonadism characterized?

    <p>High gonadotrophin concentrations with ovarian failure</p> Signup and view all the answers

    Which of the following conditions is commonly associated with amenorrhoea?

    <p>Cushing’s syndrome</p> Signup and view all the answers

    What indicates ovulation in a blood test during the menstrual cycle?

    <p>High progesterone levels</p> Signup and view all the answers

    What hormone is primarily responsible for stimulating the maturation of ovarian follicles during the follicular phase?

    <p>Follicle-stimulating hormone (FSH)</p> Signup and view all the answers

    What is the primary characteristic of hirsutism?

    <p>Excessive hair growth in a male distribution</p> Signup and view all the answers

    Which hormone is considered the most important androgen?

    <p>Testosterone</p> Signup and view all the answers

    What is the primary action of luteinizing hormone (LH) during ovulation?

    <p>Triggering the rupture of the dominant follicle</p> Signup and view all the answers

    What happens to the corpus luteum if the ovum is not fertilized?

    <p>It degenerates and leads to a drop in hormone levels</p> Signup and view all the answers

    What is a common cause of virilism?

    <p>Adrenal or ovarian tumour</p> Signup and view all the answers

    How is primary infertility defined?

    <p>Inability to achieve pregnancy after one year of unprotected intercourse</p> Signup and view all the answers

    During which phase of the menstrual cycle does oestradiol concentration rise significantly?

    <p>Luteal phase</p> Signup and view all the answers

    How many follicles are typically present in the ovaries at the onset of puberty?

    <p>100,000 to 200,000</p> Signup and view all the answers

    Which of the following conditions is considered the most common cause of anovulatory infertility?

    <p>Polycystic ovary syndrome (PCOS)</p> Signup and view all the answers

    What triggers the surge of LH release during the menstrual cycle?

    <p>The rapid increase in oestradiol concentration</p> Signup and view all the answers

    What may be elevated in individuals with polycystic ovary syndrome?

    <p>Plasma insulin concentrations</p> Signup and view all the answers

    What is the principal hormone of the luteal phase responsible for preparing the endometrium for implantation?

    <p>Progesterone</p> Signup and view all the answers

    What does virilism typically not include?

    <p>Increase in body fat</p> Signup and view all the answers

    Which of the following symptoms is typically not associated with infertility investigation?

    <p>Excessive weight loss</p> Signup and view all the answers

    What initiates the positive feedback mechanism that leads to ovulation?

    <p>Rapid rise of oestradiol</p> Signup and view all the answers

    What does a low plasma progesterone concentration of < 30 nmol/L indicate?

    <p>Ovulatory failure</p> Signup and view all the answers

    What results suggest hypogonadotrophic hypogonadism?

    <p>Decreased FSH, LH, and oestrogen</p> Signup and view all the answers

    What indicates normal response to a GnRH injection?

    <p>Plasma LH and FSH levels are doubled from basal levels</p> Signup and view all the answers

    Why should hyperprolactinaemia be excluded in infertility assessments?

    <p>It inhibits normal GnRH release</p> Signup and view all the answers

    What does a low concentration of Anti-Müllerian hormone (AMH) suggest?

    <p>Poor ovarian reserve</p> Signup and view all the answers

    What is the significance of measuring plasma FSH and LH simultaneously?

    <p>To evaluate ovarian and pituitary function</p> Signup and view all the answers

    What hormonal measurement is performed on day 21 of the cycle to assess ovulation?

    <p>Plasma progesterone concentration</p> Signup and view all the answers

    What is a common indicator of ovarian failure in plasma results?

    <p>High FSH and LH with low oestrogen</p> Signup and view all the answers

    What clinical feature is commonly associated with hirsutism?

    <p>Excessive growth of male-pattern hair</p> Signup and view all the answers

    Which hormonal change is often observed in individuals with polycystic ovary syndrome (PCOS)?

    <p>Increased testosterone and androstenedione levels</p> Signup and view all the answers

    What is a common psychological effect of virilism?

    <p>Mood swings and irritability</p> Signup and view all the answers

    In cases of infertility, which feature is evaluated during the examination?

    <p>Signs of hirsutism or virilism</p> Signup and view all the answers

    What role does decreased SHBG concentration play in individuals with obesity?

    <p>It increases free testosterone concentration.</p> Signup and view all the answers

    Which of the following is NOT a common cause of virilism?

    <p>Familial hirsutism</p> Signup and view all the answers

    What is typically elevated in women with PCOS?

    <p>Plasma insulin concentrations</p> Signup and view all the answers

    Which symptom is unlikely to be associated with hirsutism?

    <p>Abnormal ovarian morphology</p> Signup and view all the answers

    What phase of the menstrual cycle is characterized by rising levels of oestradiol and the development of follicles?

    <p>Follicular phase</p> Signup and view all the answers

    What role does gonadotrophin-releasing hormone (GnRH) play in the reproductive system?

    <p>It regulates the secretion of pituitary gonadotrophins.</p> Signup and view all the answers

    What triggers the surge in luteinizing hormone (LH) necessary for ovulation?

    <p>Rise in plasma oestradiol concentration</p> Signup and view all the answers

    Which hormone primarily stimulates the proliferation of breast epithelial cells?

    <p>Prolactin</p> Signup and view all the answers

    What role does progesterone play during the luteal phase of the menstrual cycle?

    <p>Prepares endometrium for implantation</p> Signup and view all the answers

    What is the primary source of oestrogens in females?

    <p>Ovarian follicles</p> Signup and view all the answers

    What happens to the corpus luteum if fertilization does not occur after ovulation?

    <p>It undergoes regression</p> Signup and view all the answers

    During which phase is a small number of follicles selected for development, but typically only one becomes mature?

    <p>Follicular phase</p> Signup and view all the answers

    In the context of hormone secretion, what distinguishes prolactin from other pituitary hormones?

    <p>Its secretion is inhibited by dopamine.</p> Signup and view all the answers

    Which hormone is converted from androgens in the granulosa cells of the ovaries?

    <p>Oestrogen</p> Signup and view all the answers

    What is the main consequence of high TRH concentrations in severe hypothyroidism?

    <p>Stimulation of prolactin secretion</p> Signup and view all the answers

    Which hormone is primarily responsible for the development of female secondary sex characteristics?

    <p>Oestrogens</p> Signup and view all the answers

    What signifies the onset of menstruation?

    <p>Regression of the corpus luteum</p> Signup and view all the answers

    What is the main androgen secreted by the ovaries?

    <p>Androstenedione</p> Signup and view all the answers

    What characteristic defines the luteal phase of the menstrual cycle?

    <p>Secretion of oestradiol and progesterone</p> Signup and view all the answers

    What condition might arise from impairment of hypothalamic control of prolactin secretion?

    <p>Hyperprolactinaemia</p> Signup and view all the answers

    What volume must a semen analysis be at least to be considered adequate?

    <p>2 mL</p> Signup and view all the answers

    What is indicated by raised plasma FSH and LH concentrations with low testosterone in a male patient?

    <p>Testicular problem</p> Signup and view all the answers

    What does a lack of rise in plasma LH and FSH levels after a GnRH injection suggest?

    <p>Pituitary hypofunction</p> Signup and view all the answers

    What hormonal test may be necessary to assess potential hyperprolactinaemia in males?

    <p>Plasma prolactin measurement</p> Signup and view all the answers

    Why would a human chorionic gonadotrophin (hCG) stimulation test be indicated in a male?

    <p>To assess Leydig cell function</p> Signup and view all the answers

    What characterizes oligospermia in relation to plasma FSH levels?

    <p>Low FSH suggesting pituitary disease</p> Signup and view all the answers

    What does a normal response to a GnRH test entail?

    <p>Significant doubling of LH and FSH levels</p> Signup and view all the answers

    What minimum percentage of motile spermatozoa is required in a semen analysis at 4 hours post-ejaculation?

    <p>50%</p> Signup and view all the answers

    What does a plasma progesterone concentration within the reference range during the second half of the menstrual cycle indicate?

    <p>The patient has ovulated.</p> Signup and view all the answers

    Which condition is characterized by high gonadotrophin concentrations in plasma due to ovarian failure?

    <p>Hypergonadotrophic hypogonadism</p> Signup and view all the answers

    What hormonal change occurs following the cessation of negative feedback to the pituitary after menopause?

    <p>Oestrogen levels significantly decrease.</p> Signup and view all the answers

    What typically causes secondary amenorrhoea in women?

    <p>Illness or weight loss</p> Signup and view all the answers

    What is the primary distinction between primary amenorrhoea and secondary amenorrhoea?

    <p>Primary amenorrhoea occurs when menstruation has never been established.</p> Signup and view all the answers

    In which phase of the menstrual cycle is progesterone typically measured to assess ovulation status?

    <p>Luteal phase</p> Signup and view all the answers

    What findings are similar to those of primary gonadal failure post-menopause?

    <p>High LH and FSH but low oestrogen</p> Signup and view all the answers

    What does a value in the follicular phase range of plasma progesterone indicate?

    <p>Absence of ovulation</p> Signup and view all the answers

    What hormone primarily stimulates the production of hormones by the gonads?

    <p>Luteinizing hormone (LH)</p> Signup and view all the answers

    Which of the following hormones is primarily secreted by the corpus luteum?

    <p>Progesterone</p> Signup and view all the answers

    What is the primary function of prolactin in the reproductive system?

    <p>Induces milk production in breast epithelial cells</p> Signup and view all the answers

    What is the consequence of impaired hypothalamic control over prolactin secretion?

    <p>Hyperprolactinaemia</p> Signup and view all the answers

    Which hormone is most important for the development of female secondary sex characteristics?

    <p>Oestrogens</p> Signup and view all the answers

    What is the primary role of follicle stimulating hormone (FSH) in the reproductive system?

    <p>Stimulates the development of germ cells</p> Signup and view all the answers

    How are androgens converted into oestrogens in the ovaries?

    <p>In the granulosa cells</p> Signup and view all the answers

    What differentiates the secretion of prolactin from other pituitary hormones?

    <p>Its secretion is inhibited by dopamine.</p> Signup and view all the answers

    What biochemical change occurs in plasma hormone concentrations after menopause?

    <p>Decreased concentrations of oestrogens and increased FSH</p> Signup and view all the answers

    What is indicated by a low plasma progesterone concentration taken during the second half of the menstrual cycle?

    <p>Absence of ovulation</p> Signup and view all the answers

    In cases of hypergonadotrophic hypogonadism, what would you expect to find in the plasma gonadotrophin concentrations?

    <p>High pituitary gonadotrophins with low oestrogens</p> Signup and view all the answers

    What classification of amenorrhoea occurs when a patient has never menstruated?

    <p>Primary amenorrhoea</p> Signup and view all the answers

    Which condition may lead to elevated plasma gonadotrophin concentrations?

    <p>Primary ovarian failure</p> Signup and view all the answers

    Which factor is most commonly associated with secondary amenorrhoea?

    <p>Pregnancy</p> Signup and view all the answers

    What hormonal change is expected following the atrophy of all follicles during menopause?

    <p>Decreased oestrogens and increased LH levels</p> Signup and view all the answers

    Which symptom is least likely to be directly associated with gonadal dysfunction in women?

    <p>Frequent headaches</p> Signup and view all the answers

    What primarily drives the increase in secretion of LH and FSH at the onset of the menstrual cycle?

    <p>Low concentrations of oestradiol</p> Signup and view all the answers

    During which phase of the menstrual cycle does the formation of the corpus luteum primarily occur?

    <p>Luteal phase</p> Signup and view all the answers

    What is the primary hormone secreted by the corpus luteum?

    <p>Progesterone</p> Signup and view all the answers

    Which of the following accurately describes the role of oestradiol during the menstrual cycle?

    <p>It promotes development of female secondary sex characteristics.</p> Signup and view all the answers

    What triggers ovulation approximately 16 hours after the surge?

    <p>Surge of LH release from the anterior pituitary</p> Signup and view all the answers

    What happens to the developing follicles during the follicular phase of the menstrual cycle?

    <p>Only one follicle usually reaches maturity</p> Signup and view all the answers

    What is the main role of progesterone during the menstrual cycle?

    <p>Prepare the endometrium for implantation</p> Signup and view all the answers

    What changes occur in plasma hormone concentrations if the ovum is not fertilized?

    <p>Regress of the corpus luteum and fall in hormone levels</p> Signup and view all the answers

    What does a plasma progesterone concentration of more than 100 nmol/L indicate?

    <p>Pregnancy</p> Signup and view all the answers

    What results indicate that pituitary hypofunction is present during a GnRH test?

    <p>LH and FSH levels do not rise from basal levels</p> Signup and view all the answers

    Which condition is associated with increased plasma FSH and LH while oestrogen decreases?

    <p>Hypergonadotrophic hypogonadism</p> Signup and view all the answers

    What should be considered if there is an abnormal plasma prolactin concentration in relation to infertility?

    <p>Inhibition of gonadal steroid hormone synthesis</p> Signup and view all the answers

    Which test is important for assessing both ovarian reserve and potential infertility issues?

    <p>Serum Anti-Müllerian hormone (AMH) measurement</p> Signup and view all the answers

    Which fact about thyroid function testing is true in relation to infertility?

    <p>Primary hypothyroidism can increase prolactin secretion</p> Signup and view all the answers

    Which of the following is a sign of oligomenorrhoea or amenorrhoea in relation to anovulatory infertility?

    <p>Absence of luteal phase activity</p> Signup and view all the answers

    What is the significance of measuring plasma concentrations of FSH and LH together?

    <p>To diagnose disorders of the hypothalamus or ovaries</p> Signup and view all the answers

    What does hypergonadotrophic hypogonadism indicate regarding testosterone levels and gonadotropin concentrations?

    <p>Low testosterone and high FSH and LH concentrations</p> Signup and view all the answers

    What might a low concentration of plasma FSH and LH suggest in the context of male infertility?

    <p>Pituitary or hypothalamic disease</p> Signup and view all the answers

    Which outcome from a GnRH stimulation test would suggest normal pituitary function?

    <p>Doubling of LH and FSH levels from basal levels after injection</p> Signup and view all the answers

    What condition does a raised plasma FSH concentration compared to LH indicate?

    <p>Sertoli cell failure and potential tubular failure</p> Signup and view all the answers

    In cases of suspected testicular absence, which test can be particularly useful?

    <p>hCG stimulation test</p> Signup and view all the answers

    Which of the following measurements can help exclude thyroid disease in male infertility assessments?

    <p>Thyroid function test</p> Signup and view all the answers

    What does azoospermia indicate in the context of male fertility investigations?

    <p>Absence of sperm in the ejaculate</p> Signup and view all the answers

    What is the expected time frame for a detectable rise in plasma testosterone after administering hCG?

    <p>72-120 hours</p> Signup and view all the answers

    Study Notes

    Luteal Phase

    • The luteal phase of the menstrual cycle is characterized by the production of progesterone and estrogen by the corpus luteum formed from the ruptured follicle after ovulation
    • Progesterone prepares the endometrium for implantation of a fertilized ovum and is crucial for early pregnancy maintenance.
    • The luteal phase also increases basal body temperature.

    Testosterone

    • Testosterone is produced by Leydig cells in the testes.
    • Its production is stimulated by luteinizing hormone (LH).
    • Testosterone, in turn, inhibits LH secretion by negative feedback.
    • Testosterone is essential for male sexual differentiation, development of secondary sexual characteristics, spermatogenesis, and anabolism.
    • In target cells, testosterone is converted to dihydrotestosterone, a more potent androgen, by the enzyme 5-α-reductase.

    Inhibin

    • Inhibin is produced by Sertoli cells in the seminiferous tubules during germ cell differentiation and spermatogenesis.
    • Inhibin controls follicle-stimulating hormone (FSH) secretion through negative feedback.

    Gonadotropins

    • Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) regulate testicular function.

    Hyperprolactinemia

    • Hyperprolactinemia can lead to amenorrhea, sexual dysfunction, infertility, and potentially breast cancer.
    • Elevated prolactin levels inhibit GnRH release.
    • Reduced GnRH results in decreased gonadotropin secretion (LH and FSH), which in turn inhibits gonadal steroid hormone synthesis, leading to infertility.
    • This can be caused by physiological factors, such as stress or pregnancy.
    • Damage to the pituitary stalk can also contribute to hyperprolactinemia.
    • Pituitary tumors, both microadenomas and macroadenomas, can also cause hyperprolactinemia.
    • Certain medications, such as estrogens, dopaminergic antagonists, can increase prolactin.
    • Polycystic ovary syndrome, chronic kidney disease, and severe hypothyroidism can also lead to hyperprolactinemia.

    Normal Female Gonadal Function

    • During puberty, gonadotropin secretion increases, leading to rising ovarian estrogen production.
    • This promotes the development of female secondary sex characteristics and the onset of menstruation.
    • The ovaries contain around 100,000 – 200,000 follicles at puberty.
    • During each menstrual cycle, several follicles start to develop, but typically only one matures and is released as an ovum (ovulation).

    Menstrual Cycle Phases

    • Follicular (Pre-Ovulatory) Phase: At the beginning of the cycle, follicles are undeveloped, and estrogen levels are low. LH and FSH secretion increases due to reduced negative feedback from estrogens. The dominant follicle becomes more sensitive to FSH and matures while others atrophy. LH stimulates estrogen production, leading to endometrial regeneration.
    • Ovulation: Rapid development of the dominant follicle and increasing estrogen levels trigger a surge in LH release (positive feedback). Ovulation occurs about 16 hours later.
    • Luteal (Post-Ovulatory or Secretory) Phase: High LH levels stimulate the granulosa cells of the ruptured follicle to luteinize, forming the corpus luteum which produces progesterone and estrogen. Progesterone is the dominant hormone during this phase and prepares the endometrium for implantation. If fertilization doesn't occur, the corpus luteum regresses, and ovarian hormone levels fall, leading to menstruation.

    Menopause

    • Menopause is the permanent cessation of menstruation, typically around age 50.
    • Menopause occurs when all follicles have atrophied.
    • Estrogen levels decline, while FSH and LH levels increase due to the removal of negative feedback from the ovaries.
    • This resembles primary gonadal failure (ovarian failure).

    Disorders of Gonadal Function in Females

    • Gonadal dysfunction in females usually presents with amenorrhea, hirsutism, virilism, or infertility.

    Amenorrhea

    • Amenorrhea is the absence of menstruation.
    • It can be caused by hormonal abnormalities.
    • In ovarian failure, pituitary gonadotropin levels are high (hypergonadotrophic hypogonadism).
    • When the cause is in the hypothalamus or pituitary, gonadotropin secretion is reduced (hypogonadotrophic hypogonadism).
    • Primary amenorrhea occurs when menstruation has never begun and is often associated with delayed puberty.
    • Secondary amenorrhea occurs when established menstrual cycles cease and is commonly due to physiological factors such as pregnancy, menopause, severe illness, rapid weight loss, and stopping oral contraceptives.
    • Endocrine disorders such as hyperprolactinemia, hyperthyroidism, Cushing’s syndrome, and acromegaly can also cause amenorrhea.

    Hirsutism and Virilism

    • Increased plasma free androgen concentrations or increased tissue sensitivity to androgens lead to effects ranging from excess hair growth (hirsutism) to marked masculinization (virilism).
    • Testosterone is the primary androgen.
    • Hirsutism is excessive hair growth in a male distribution and is common, potentially affecting 10% of women. Causes include familial hirsutism, polycystic ovary syndrome, adrenal or ovarian tumors, Cushing’s syndrome, and exogenous androgen drugs.
    • Virilism is characterized by masculinizing symptoms, including increased male-pattern hair growth, deepening of the voice, and breast atrophy. It always involves high plasma androgen levels and often elevated DHEA (dehydroepiandrosterone). Common causes include adrenal or ovarian tumors, Cushing’s syndrome, and exogenous androgen drugs.

    Polycystic Ovary Syndrome (PCOS)

    • PCOS is a condition characterized by hyperandrogenism, anovulation, and abnormal ovarian morphology - the most common cause of anovulatory infertility.
    • Symptoms include hirsutism, menstrual irregularities, enlarged polycystic ovaries, and infertility.
    • Plasma testosterone and androstenedione levels are often elevated.
    • LH may be increased with normal FSH.
    • Free testosterone levels are frequently elevated in obese individuals due to reduced SHBG (sex hormone-binding globulin) concentrations.
    • Prolactin levels can also be high.
    • Ultrasound scans may reveal multiple small subcapsular ovarian cysts.
    • PCOS is associated with insulin resistance, obesity, and elevated plasma insulin levels.
    • It can also present with hyperlipidemia, glucose intolerance, and hypertension.

    Infertility

    • Primary infertility refers to the inability to conceive after at least 1 year of unprotected intercourse.
    • Secondary infertility occurs when there has been a previous pregnancy.
    • A normal menstrual cycle doesn't guarantee fertility (about 95% of such cycles are ovulatory).
    • Anovulatory infertility is a common cause of female infertility and is associated with irregular periods (oligomenorrhea) or absence of periods (amenorrhea).

    Investigations of Female Infertility

    • Plasma progesterone measurement in the luteal phase (day 21): This test helps determine if ovulation has occurred. Normal progesterone levels indicate ovulation, while low levels suggest ovulatory failure. Progesterone levels exceeding 100nmol/L suggest pregnancy.
    • Plasma FSH, LH, and estrogen levels:
      • Increased FSH and LH with decreased estrogen suggests hypergonadotrophic hypogonadism (ovarian failure).
      • Decreased FSH, LH, and estrogen suggests hypogonadotrophic hypogonadism (pituitary or hypothalamic disease).
    • GnRH test: This test involves intravenous injection of GnRH followed by measuring LH and FSH levels.
      • Normal response: LH and FSH levels double from their basal levels.
      • Pituitary hypofunction: LH and FSH levels fail to rise.
      • Hypothalamic disease: LH and FSH levels show an exaggerated response.
    • Plasma prolactin level: This test helps rule out hyperprolactinemia, which can inhibit GnRH release and lead to infertility.
    • Thyroid function test: This test helps exclude thyroid disease. Severe hypothyroidism can increase prolactin.
    • Ovarian ultrasound: This examination monitors follicular development and ovulation and helps rule out PCOS.
    • Anti-Müllerian Hormone (AMH) levels: Low serum AMH levels indicate poor ovarian reserve (the size of the ovarian ovum supply). AMH may be useful in the investigation of infertility.

    The Reproductive System

    • Responsible for the production of hormones and maturation of germ cells in the gonads

    Hypothalamic Hormones

    • The hypothalamus secretes Gonadotropin-Releasing Hormone (GnRH), which regulates the secretion of the pituitary gonadotropins: Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH).
    • The hypothalamus also secretes dopamine, a neurotransmitter that controls prolactin secretion.

    Anterior Pituitary Hormones

    • The Pituitary gland secretes LH and FSH which control the function and secretion of gonadal hormone production.
    • LH primarily stimulates the production of hormones by the gonads.
    • FSH stimulates the development of germ cells
    • Prolactin is secreted by pituitary cells and stimulates breast epithelial proliferation and milk production.
    • Prolactin's secretion is inhibited by dopamine, therefore, impaired hypothalamic control causes hyperprolactinemia.

    Ovarian Hormones

    • Oestrogens (C18 steroids), progesterone, and androgens (C19 steroids) are secreted by the ovaries
    • Oestradiol is the most important ovarian oestrogen and is converted to oestrone in the liver and subcutaneous fat
    • Androstenedione is the main androgen secreted by the ovaries and is converted to oestrone and testosterone
    • Testosterone is secreted in smaller amounts directly by the ovaries.

    Normal Female Gonadal Function

    • At puberty, an increase in gonadotropin secretion leads to an increase in oestrogen secretion.
    • This triggers the development of secondary sex characteristics, and the onset of menstruation.
    • The ovaries contain 100 000 to 200 000 follicles that develop during the menstrual cycle, and usually only 1 reaches maturation
    • The mature follicle is released from the ovary as an ovum (ovulation).

    The Menstrual Cycle

    • The process of ovulation occurs over three phases: the follicular phase, ovulation, and the luteal phase.
    • Follicular Phase - ovarian follicles are undeveloped and plasma oestradiol concentrations are low. An increase in LH and FSH stimulates the growth of follicles, and one becomes dominant and matures. Plasma oestradiol concentrations rise, stimulating endometrial regeneration.
    • Ovulation - the rise in plasma oestradiol concentration triggers a surge in LH from the anterior pituitary, which occurs approximately 16 hours later.
    • Luteal Phase - the increase in LH causes the ruptured follicle to form the corpus luteum, which synthesises and secretes progesterone and oestradiol. Progesterone is the main hormone in this phase and prepares the endometrium for the implantation of a fertilised ovum.
    • If the ovum isn't fertilized, the Corpus Luteum regresses and plasma ovarian hormone concentrations decrease, leading to menstrual bleeding due to the sloughing of the endometrium.

    The Menopause

    • Occurs when all follicles have atrophied.
    • Plasma concentrations of oestrogens decrease, FSH and LH (to a lesser extent) increase.

    Disorders of Gonadal Function in Females

    • Symptoms include amenorrhoea, hirsutism, virilism, and infertility.

    Amenorrhoea

    • Defined as the absence of menstruation; it can be due to hormonal abnormalities.
    • High gonadotrophin concentrations in plasma (hypergonadotrophic hypogonadism) reflect ovarian failure.
    • Primary amenorrhoea is when a patient has never menstruated, typically associated with delayed puberty.
    • Secondary amenorrhoea is when previously established menstrual cycles have ceased, which is most often due to physiological factors, such as pregnancy or menopause.
    • Other causes: severe illness, excessive weight loss (anorexia nervosa), stopping oral contraceptives.

    Hirsutism & Virilism

    • Increased plasma free androgen concentrations, or increased tissue sensitivity to androgens, can lead to excessive hair growth (hirsutism) and marked masculinization (virilism).
    • Hirsutism refers to excessive hair growth in a male distribution and can be familial or caused by conditions like polycystic ovary syndrome, adrenal or ovarian tumors, Cushing's syndrome, and exogenous androgens.
    • Virilism includes hair growth in a male pattern, deepening of the voice, and breast atrophy, due to increased plasma androgen concentrations. Common causes include adrenal or ovarian tumors, Cushing’s syndrome, and administration of exogenous androgens.

    Polycystic Ovary Syndrome (PCOS)

    • The most common cause of anovulatory infertility.
    • Features include hyperandrogenism, anovulation, and abnormal ovarian morphology.
    • Symptoms include hirsutism, menstrual disturbances, enlarged polycystic ovaries, and infertility.
    • Plasma testosterone and androstenedione concentrations are frequently increased.
    • Plasma LH may be elevated with normal FSH, and plasma prolactin concentrations may be high.
    • Ultrasound scanning can reveal multiple subcapsular ovarian cysts.
    • PCOS is also associated with insulin resistance, obesity, elevated plasma insulin concentrations, hyperlipidaemia, glucose intolerance, and hypertension.

    Infertility

    • Primary Infertility is when conception has never occurred despite at least 1 year of unprotected intercourse.
    • Secondary Infertility is when there has been a previous successful or unsuccessful pregnancy.
    • Examination should include checking for hirsutism, virilism, galactorrhoea.

    Investigations of Female Infertility

    • Plasma progesterone concentrations should be measured in the second half of the menstrual cycle, typically on day 21. A value within the reference range for that time of the cycle indicates ovulation.

    Disorders of Gonadal Function in Males

    • Investigations of Male Infertility

    Semen Analysis

    • Volume of at least 2 mL.
    • At least 20 × 109/L spermatozoa, with over 50% being motile 4 hours post ejaculation.
    • At least 30% have normal morphology.

    Plasma Testosterone, LH, and FSH Concentrations

    • Elevated plasma FSH and LH with low testosterone (hypergonadotrophic hypogonadism) indicates a testicular problem like Leydig cell failure.
    • Low plasma FSH, LH, and testosterone suggests pituitary or hypothalamic disease (hypogonadotrophic hypogonadism).
    • Increased plasma FSH compared to LH may indicate seminiferous tubular failure (Sertoli cell failure), regardless of the plasma testosterone concentration. This often results in azoospermia or oligospermia.
    • Low plasma FSH with oligospermia may suggest pituitary or hypothalamic disease.
    • If plasma gonadotrophin concentrations (FSH and LH) are low, a GnRH test may be required.
    • In an intravenous GnRH test, plasma LH and FSH concentrations are measured before and after GnRH injection. A normal response is a doubling of the plasma LH and FSH levels from their baseline. No response suggests pituitary hypofunction, and an exaggerated response may suggest hypothalamic disease.

    Other Important Investigations for Male Infertility

    • Prolactin should be measured to rule out hyperprolactinemia.
    • Thyroid function tests should be conducted to exclude thyroid disease.
    • A Human Chorionic Gonadotrophin (hCG) stimulation test may be indicated to assess Leydig cell reserve.

    The Reproductive System

    • Responsible for the production of hormones and maturation of sex cells (germ cells) in the gonads.
    • Influenced by hypothalamic and anterior pituitary hormones.

    Hypothalamic Hormones

    • Gonadotropin-releasing hormone (GnRH) stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland.
    • Dopamine serves as a neurotransmitter and regulates prolactin secretion.

    Anterior Pituitary Hormones

    • LH and FSH control hormonal function in the testes and ovaries.
    • LH primarily stimulates hormone production by the gonads.
    • FSH promotes germ cell development.
    • Prolactin stimulates breast growth and milk production.
    • Prolactin secretion is inhibited by dopamine.
    • Disruptions in hypothalamic control can lead to hyperprolactinemia.

    Ovarian Hormones

    • Ovaries produce estrogens, progesterone, and androgens.
    • Androgens are synthesized by theca cells and converted into estrogens by granulosa cells.
    • Estradiol is the most significant ovarian estrogen.
    • Oestrogens promote development of female secondary sex characteristics and regulate menstruation.
    • Progesterone is secreted by the corpus luteum and contributes to endometrial preparation during the menstrual cycle.

    Thyroid-Releasing Hormone (TRH)

    • Stimulates prolactin and thyroid-stimulating hormone (TSH) secretion.
    • May play a role in pathological conditions but doesn't have a significant physiological effect.

    Normal Female Gonadal Function

    • Gonadotropin secretion rises at puberty, stimulating the development of female secondary sex characteristics and initiating menstruation.
    • The ovaries contain a large number of follicles, but typically only one matures per menstrual cycle.
    • The menstrual cycle consists of three phases: Follicular, Ovulation, Luteal.

    Follicular Phase

    • Starts with undeveloped follicles and low estradiol levels.
    • Increased LH and FSH levels stimulate follicle growth.
    • One follicle dominates and matures, while others atrophy.
    • Estradiol levels rise, leading to endometrial regeneration.

    Ovulation

    • A surge in LH is triggered by the development of the dominant follicle and increased estradiol levels.
    • Ovulation occurs about 16 hours after the LH surge.

    Luteal Phase

    • The corpus luteum forms after ovulation.
    • The corpus luteum produces progesterone and estradiol.
    • Progesterone is the main hormone during the luteal phase and prepares the endometrium for implantation.
    • If fertilization doesn't occur, the corpus luteum regresses, hormones decline, and menstruation takes place.

    Menopause

    • Permanent cessation of menstruation.
    • Occurs when the ovaries lose all follicles.
    • Estrogen levels decline, while FSH and LH levels rise.
    • Similar hormonal profiles to primary gonadal failure (ovarian failure).

    Disorders of Gonadal Function in Females

    • Often present with amenorrhea, hirsutism, virilism, and infertility.

    Amenorrhea

    • The absence of menstruation.
    • Causes include hormonal abnormalities, ovarian failure (hypergonadotrophic hypogonadism), or pituitary/hypothalamic issues (hypogonadotrophic hypogonadism).
    • Primary: No menstruation ever occurring.
    • Secondary: Cessation of previously established menstrual cycles.

    Anovulatory Infertility

    • Common form of female infertility.
    • Associated with irregular or absent menstrual cycles.
    • Investigation includes measuring plasma progesterone levels during the luteal phase (day 21) and evaluating FSH, LH, and estrogen levels.
    • GnRH stimulation testing can identify pituitary or hypothalamic dysfunction.
    • Hyperprolactinemia, thyroid disorders, and polycystic ovary syndrome should be ruled out.
    • Monitoring follicular development and ovulation with ultrasound scans is important.
    • Anti-Müllerian hormone (AMH) is released by granulosa cells and can indicate ovarian reserve.

    Disorders of Gonadal Function in Males

    • Investigated through semen analysis and hormone testing.

    Semen Analysis

    • Assess sperm count, motility, and morphology.
    • Normal values include at least 2 mL volume, more than 20 billion sperm/L, 50%+ motility 4 hours after ejaculation, and 30%+ normal morphology.

    Hormone Testing

    • Plasma testosterone, LH, and FSH levels are measured.
    • Hypergonadotrophic hypogonadism: high FSH/LH, low testosterone, indicates testicular problems.
    • Hypogonadotrophic hypogonadism: low FSH/LH and testosterone, suggests pituitary or hypothalamic disease.
    • Elevated FSH compared to LH may indicate Sertoli cell failure and azoospermia/oligospermia.
    • GnRH stimulation test is used to assess pituitary and hypothalamic function.
    • Hyperprolactinemia and thyroid disorders are excluded by testing.
    • hCG stimulation test assesses Leydig cell reserve.

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    Description

    This quiz covers key concepts related to the luteal phase of the menstrual cycle, testosterone production, and the role of inhibin in male reproductive physiology. Test your understanding of hormonal functions and their implications for reproduction and development.

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